1. Field of the Invention
Stable foam structures can have a wide variety of uses. They can act as supports for catalysts, providing for a high surface to volume ratio. Depending on the material employed, they can act as coalescing agents for oil-in-water emulsions or as filtering devices. Because of the high strength to weight ratios which are possible, foam structures can act in various constructions as lightweight building materials, such as in air frames or, where weight is of significant concern. In addition, the materials can act as supports for a variety of other materials with which they may or may not react. Also, the reticulated foam structures may find use as solid propellant reinforcement and burning rate modifiers, battery plates, electrochemical anodes and cathodes, heat shields, heat exchanger cores, sound or shock absorbers, anodic protectors, flame guards, liquid reservoirs, micro-wave reflectors, radiation shields, wicks, etc.
In many of the uses for reticulated structures, it is desirable or necessary that these structures be relatively free of closed cells. Furthermore, a relatively uniform structure is desirable, so that pore sizes do not differ to any significant extent. In addition, for commercial manufacture, the method should permit a relatively reproducible means for forming structures of substantially uniform dimensions and properties.
2. Description of the Prior Art
Numerous patents have been issued describing a variety of ways of making open pore cellular foam of materials such as metals, metal alloys, metal oxides, ceramics, glasses and the like. Included among these patents are U.S. Pat. Nos. 3,052,967, 3,090,094, 3,111,396, 3,362,818, 3,408,180 and 3,470,117. See U.S. Pat. No. 3,171,820 for preparation of reticulated polyurethane foam.